thompson



ELECTRIC CABLE.

Patented Nov. 17, 1896.

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' WWNESSES I INV ENTOR fi/f vi v 2 Sheets-Sheet 2.

(N0 Model.)

S. P. THOMPSON.

' BLEGTRIO CABLE. 571,707. Patented Nov. 17, 1896 WlTNE SSES NVENTOR "4, 1893; in France, No. 222,460, dated J une UNITED STATES PATENT Orricn.

'SILVANUS PHIL IPS THOMPSON, or LONDON, ENGLAND.

ELECTRIC i cAeLs."

SPECIFICATION forming part of Letters TPatent No. 571,707, dated. November 17, 1896. Application filed July 20, 1892. Serial No. 440,673- (No this.) Patented in England December 21, 1891. No. 22,304 and July 4,18%,170. 13,084 5 in France June 20, 1892.

23. 1892, No, 86,013; in India. April25,1893, No, 320,

l3,896 and April 10, 1894, No. 15,806; in Brsail February 7,

Straits Settlements December 14, 1895. v

To all whom it 11ml P01116077):

Be it known that I, SILVANU s PHILLIPS THOMPSON, doctor of science, a subject of the Queen of Great Britain, residing at Morland, Ghislett Road, lVest Hampstead', London, in the county of Middlesex, Eugland,-have invented certain new and. useful Improvements in Electric Cables, (for which I have obtained patents in Great. Britain No. 22,304,- dated December 21,1891, and No, 13,06a,-dated July g 20, 1892, and No. 234,763, dated December 13,

1833; in Germany, No. 86,013, dated October 23, 1892; in Spain, No. 13,896, dated Septemher 4, 1893, and No. 15,306, dated. April '10,

India,- No. 320, dated April 25, 1893, and No: 18, dated August 17, 1894; in Brazil, No. 1,686, dated February 7, 1891; in Ceylon,

No. 443, dated August 22, 1894, and in Straits. Settlements, dated December. 14, 1895,) of

which the following is a specification;

My invention pertains to electric signaling for telegraphic, telephonic, or other purposes through long lines or cables, and has for its chief objects to extend the distance to which such signaling can be carried on and to in crease the rapidity and facility of signalin By signaling I mean the communicating of any sort of signals, whether spoken words, as in telephonic signaling,or liummin g sounds, as in harmonic telegraphs, or rapidly-reversed impulses like those used in rapid automatic telegraphy, or dot-and-dash signals due tointerruptions or reversals of current, or cleflections of a needle to right and left, or motions ofa siphon recorder or of the tongue of a relay;

As lines and cables are now constructed there is a practical limit to the distance to.

which signaling is possible with existing instruments. My invention will increase this distance. There is also for a line or cable of given length as at present constructed a limit to the rapidity at-which signals can 'be sent kind of instrument that can be used to'siglie. 222,460, and December 13, 1898, No. 234,763; in Germany October and August 17,1894,No. 18 i in Spain September 4, 1893,1io. 1894,1i0. 1,686 3h! Ceylon Augu t 22,1894, N0. 443, and in nal, high-speed instruments, harmonic telegraphs, and telephones notbeing capable of being used on long cables or on very long .lines, lily-invention WillGXtGild the facility of signaling by rendering lines and cables available for instruments for which they are not now available. It will also increase the facility of signaling through cables by'enablin g signaliiig to be carried. on without such expensi vc arrangements for securing balance, known as artificial cables,- as at present used at theshore ends.

, It is known that the presence in cables and lines of electrostatic capacity limits the rate of signaling and the distance of signaling, as well as limits the kinds of signals that can be sent to a given distance. For example,

about one-third microfarad per nautical mile, retards telegraphic signals so much that only a few words per minute can be transmitted. The distance to which rapid automatic signals can be sent through cables of this type is but a few score miles. Through very long cables of existing types telephones, harmonic telegraphs, and rapid automatic instruments cannot be used at all,

It is known that the cause of the limitations mentioned above as found with cables and long lines of existing type is the presence of electrostatic capacity, Such electrostatic capacity is in general not located at any one point,but is distributed more or less uniformly tion 1 counterbalance the effects of this distributed capacity by applying distributed electromagnetic induction. Electromagnetic induction is the action which the rise or fall of the current in any part of the circuit produces on the same or any other part of the circuit by virtue of the fact that every varying current produces around it a varying magnetic field, When the current is varying in a wire or coil, the varying magnetic field around it induces elecromoti ve forces in neighboring conductors or coils or in other convolutions of the. same wire or cell. By proper dispositions, as hereinafter further the capacity of an Atlantic cable, which is along the line or circuit. Now by my invensuch cases the retarding and limiting effects," I though not entirely neutralized, will be di",

minished.

Now my present invention consists in dividing or virtually dividing the entire distance through which the signals have to be cut into a series of shorter circuits conne ted with each other by the aid of double induction-coils or other devices for producing mutual induction between the parts, so that each circuit in turn induces acurrent in the next. The essence of the sectioning of the cable is that, since retardation results from there bein g a capacity distributed along a great length, one should so modify the system that movements of electricity to efi'ect the charges and discharges of the accumulations in the cable can'take place over short lengths of circuit instead of having to fiow in and out from the ends up to the places where the charge has accumulated. o

. In those cases where coils are employed, if iron cores be used for the coils, they must be small in quantity and well laminated. In cases where these coils are connected across the two lines of the conductors within the cable they shall preferably have a i'elatively high resistance and a high time constant. These coils should have each such dimensions and be made with such a number of turns of wire of such a gage wound around a welllaminated iron core of such shape and length that the-time constant (or interval of time that is needful for the current in the said coil to rise to 0.634 of its final value) shall be not m uch less than and shall be preferably greater than one one-hundredth second, while the resistance of the said coil shall be at least as great as or greater than that of the ten or twenty mile section of the cable, and shall, indeed, in the case of long cables, be with ad vantage as great as or greater than the resistance of the entire length of the conductor. I may produce a distributive mutual inductionbetween the separate sections of a cable in various other ways.

In cases where double induction-coils are arranged in the two lines or conductors, (instead of across them,) as in Figure 5, hereinaftcr described, the coils, though they should in general have time constants and cores, as before, must be of resistance lower than that of the rest of the circuit, and their windings may with advantage be interwound, that is to say, not separated into .two coils, primary similar material.

and secondary, each apart from the other, one inside, the other outside,- or one at one end oi the core, the other at the other, but are wound between one another, so as to lie as nearly as-possible geometrically in identical relations to their core.

In some cases where cables with two condoctors are used the-actual mutual induction between adjacent parallel portions of the two conductors or lines (going and return wires) within the cable may be sufficiently utilized without inserting specific double inductioncoils, for it is well known that there is mutual induction of the electromagnetic kind even between two parallel straight conductors lying near to one another. This mutual inductioncan be increased by adding outside a wrapping of laminated iron wires wound over the insulating sheathing of gutta-percha or It may also be increased by constructing the cable so that the two wires or. conductors spiral round one another, either continuously or at intervals, a distributed mutual induction being thereby 'attained, but in all cases there should be in the designing of a cable for any given service such proportioning of mutual induction to capacity and resistance as to fulfil .for the case arising the conditions of approximate balance of effects.

Referring to the drawings, in Fig. l a se ries of circuits are connected by double induction coils or transformers C. In Fig. 2 each wire is connected to the sheath or earth by double induction-coils and the two wires can be used independently. In Fig. 3 an inner and outer conductor are employed and the outer connected by double induction-coils with the sheath or earth. "In Fig. 4' the inner and outer conductors are connected with each "other and also with the earth by double induction-coils Fig. 5, two lines wound round each other or a core at intervals to form double induction-coils; Fig. 6, two lines forming double induction-coils at intervals and one of them cutinto sections joined by condensers; Fig. 7, two conductors, one of themcontinnous, the other out into sections, the ends of which overlap sufiiciently to produce an induced current. Fig. 8 isa cable where three conductors are connected by double induction coils; Fig. 9, *where two lines are joined by double induction-coils, and a third line'is coiled in double induction manner round turn-circuits in which the conductors are scparately insulated throughout, which consists in dividing the circuit into a series of successive separately-insulatedmetallic returncircuits in each of which a movement of electricity takes place and connecting these circuits by mutual induction.

2. A cable comprising a metallic returnline formed into a series of comparatively short independent and completely-insulated circuits each-of substantially the same length .or capacity and connected by mutual induc-- tion coils, or devices, the whole being inclosed within a common sheath, substantially as de- I sulated conductors inclosed side by side within a common external sheath, one of the said conductors being continuous from end to end, and the other being actually divided, the two divided parts being arranged in inductive relation and their ends connected to the undivided conductor. 5. A cable consisting of two or more internal conductors, each of which is divided into sections constituting thereby a large number of successive circuits arranged in inductive relation each to the'nextand each inducing into the nextin succession, the lines of conductors being connected across to a continuous conductor by double induction-coils, each having a high time constant, andhaving small well-laminated iron cores.

6, A cable consisting of two internal couductors separately insulated and inclosed within a common external sheath acting with a distributive mutual induction between their own parallel portions, either of the said internal conductors being divided, actually or ,virtu a'lly, into sections in each of which a motion of electricity is possible.

4 7. In a cable consisting of two continuous metallic conductors, means for virtually dividing said conductors into connected sections, said means comprising induction devices applied dis'tributivcly to said conductors at intervals. 1

'- S. A twin-wire cable comprising an outgo 'ng and a returnline, both separately insue,

ated and inclosed'wi thin one common sheath,

the said cable being formed into a series of comparatively short independent completelyinsulated circuits each of substantially the-- same length or capacity, andconnected by mutual induction coils or devices, substantially as described.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

SILYANUS PHILLIPS THOMPSON.

\Vitnesses:

T. F. BARNES, WALTER J. SKER'EEN. 

